1. Field of the Invention
The present invention relates to a sensor (i.e. strain gage) for instantly detecting a small strain displacement and the producing method thereof.
2. Description of the Related Art
When a strain in a structural member is to be detected, a metal wire resistance strain gage whose resistance changes with respect to the strain is generally used.
This metal wire resistance strain gage is easy to handle and is highly reliable as compared with other types of sensors, and hence is widely used for measurement and detection. In general, however, the metal wire resistance strain gage has low detection sensitivity. For this reason, when the metal wire resistance strain gage is to be used for, e.g., load detection, driving force detection, or force detection for a robot or the like, the following scheme (i.e. measuring scheme) is employed to increase the level of a detected signal. In this scheme, a driving force transmitting member as a target to be detected is partially processed to have a portion in which the amount of strain is larger than that in other portions, i.e., a portion having lower mechanical rigidity, and a sensor of this type of strain gage is bonded to this portion. However, a reduction in rigidity of a driving force transmitting system of, e.g., a robot as a measurement target leads to a deterioration in response properties of the robot, and hence is not desirable. In addition, if an excessive force acts on a distal end portion of the robot, since the low-rigidity portion is greatly distorted, the sensor bonded to the portion may be distorted and destroyed permanently.
As a sensor having high sensitivity, a semiconductor strain sensor (gage) is known. Various limitations, however, are imposed on a sensor of this type in terms of handling. Therefore, this sensor is poor in versatility.
Under the circumstances, a strong demand has arisen for a strain sensor which is easy to handle and has high sensitivity and high reliability.
As described above, the conventional strain sensors cannot satisfy all the requirements, e.g., high sensitivity, easiness in handling, and high reliability.